Chicken Thighs with Lemon Sauce - Cooking like a Boss

Recipe from https://recipes.anovaculinary.com/recipe/sous-vide-chicken-thighs-with-lemon-sauce/ .

2 ²⁄₃tbsp 0.04l 40ml 8tsp 0.169cup 0.07pint olive oil	heat in skillet on med-high				sear until well browned		serve
2 ²⁄₃tbsp 0.04l 40ml 8tsp 0.169cup 0.07pint butter for searing
2400g 2 ²⁄₅kg 5.29lb 84.7oz chicken thighs	season	vac bag	sous vide 74degC for 2h	pat dry
salt for chicken
pepper for chicken
2 ²⁄₃tbsp 0.04l 40ml 8tsp 0.169cup 0.07pint butter for chicken
2 ²⁄₃ onion	chop finely	brown	simmer until thick glaze	remove from heat	whisk in slowly	season to taste
2 ²⁄₃tsp 0.013l 13 ¹⁄₃ml 0.889tbsp 0.056cup 0.023pint butter for onion
626 ²⁄₃ml 0.627l 41.8tbsp 125 ¹⁄₃tsp 2.65cup 1.1pint beef stock
173 ¹⁄₃ml 0.173l 11.6tbsp 34 ²⁄₃tsp 0.733cup 0.305pint lemon juice	whisk
5 ¹⁄₃ egg yolks